Caracterização geológica e tecnológica de argilas plásticas em rochas Permianas-Carboníferas da região de Tatuí e Porto Ferreira/SP
Carregando...
Data
2021-09-16
Autores
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
O crescente aumento da demanda por argilas plásticas a superplásticas de cor de queima clara para produção de porcelanatos e outras placas cerâmicas, somado à carência dessa matéria-prima no Estado de São Paulo, provocam a busca por novas jazidas e um melhor entendimento dos depósitos conhecidos. No Estado, as duas principais minerações (Santa Adelaide e Fazendinha), localizadas nos municípios de Tatuí e Porto Ferreira, estão inseridas no contexto do Permiano/Carbonífero da Bacia do Paraná e são produtos de alteração intempérica, posicionadas em duas situações geomorfológicas distintas: topos de morros e fundos de vale. Além dessas duas minas, foram selecionados alvos do Grupo Itararé e das formações Tatuí e Corumbataí nos municípios de Leme, Piracicaba e Tambaú para levantamento dos respectivos perfis de alteração, bem como para caracterização mineralógica, petrográfica, geoquímica e tecnológica. Os estudos de campo indicaram que as argilas superplásticas ocorrem em siltitos argilosos a arenosos, alterados, laminados a maciços, de cor cinza a verde claro. Nos fundos de vale, essas camadas estão sobrepostas por depósitos aluvionares e possuem espessura máxima de 2 metros, enquanto que nos topos de morro, especialmente na Formação Tatuí, as camadas podem apresentar até 6 metros de espessura e ocorrem em maiores profundidades, sendo sobrepostos por litotipos mais intemperizados. Os principais minerais constituintes das camadas de interesse são montmorillonita, illita, caulinita, quartzo, feldspatos alcalinos, muscovita e geralmente apresentam menores teores de Fe2O3 e maior proporção de álcalis em relação às camadas adjacentes. Os estudos cerâmicos indicaram elevado módulo de ruptura à flexão a seco (≥ 40 Kg.f/cm²) para a maioria das amostras e similaridades de fundência entre as amostras de mesma unidade litoestratigráfica, denotada pela porcentagem de absorção de água, retração linear de queima e módulo de ruptura após queima a 1.120 e 1.190 ºC . As cores de queima variaram nas tonalidades bege, cinza ou marfim, com exceção da Formação Corumbataí de Tambaú, que mostraram cores predominantemente mais escuras e avermelhadas devido ao maior teor de Fe2O3 livre. Ao final, são discutidos guias prospectivos objetivando contribuir para a descoberta de novas jazidas.
The growing demand for light-burning plastic to superplastic clays for the production of porcelain tiles and other ceramic slabs, added to the lack of this raw material in the State of São Paulo, has led to the search of new deposits and a better understanding of those already known. The two main mines of the State (Santa Adelaide and Fazendinha), located in the cities of Tatuí and Porto Ferreira, are inserted in Permian/Carboniferous units of the Paraná Basin and are products of weathering, positioned in two distinct geomorphological situations: hilltops and valley. Beyond these two mines, targets of the Itararé Group and Tatuí and Corumbataí formations in the cities of Leme, Piracicaba and Tambaú were selected to study their alteration profiles, as well as for mineralogical, petrographic, geochemical and technological characterization. Field studies indicated that plastic clays occur in weathered, laminated to solids, gray to light green clayey to sandy siltstones. At the valleys, these layers are overlaid by thin alluvial deposits and have a maximum thickness of 2 meters, while on the hilltops, especially in the Tatuí Formation, the layers can be up to 6 meters thick and occur at greater depths, being overlapped by more weathered lithotypes. The main minerals of the superplastic clay layers are constituted by montmorillonite, illite, kaolinite, quartz, alkali feldspars, muscovite and generally have lower Fe2O3 contents and a higher proportion of alkali comparing to the adjacent layers. Ceramic studies indicated high modulus of rupture in dry condition (≥ 40 Kg.f/cm²) for most samples and differences in water absorption, linear shrinkage and modulus of rupture after firing at 1.120 and 1.190°C among the lithostratigraphic units. The firing colors varied from beige to gray or ivory, excepting the Corumbataí Formation from Tambaú, which showed predominantly darker and reddish colors due to the higher content of Fe2O3 oxides/hydroxides. At the end, prospective guides are discussed in order to contribute to the discovery of new deposits.
The growing demand for light-burning plastic to superplastic clays for the production of porcelain tiles and other ceramic slabs, added to the lack of this raw material in the State of São Paulo, has led to the search of new deposits and a better understanding of those already known. The two main mines of the State (Santa Adelaide and Fazendinha), located in the cities of Tatuí and Porto Ferreira, are inserted in Permian/Carboniferous units of the Paraná Basin and are products of weathering, positioned in two distinct geomorphological situations: hilltops and valley. Beyond these two mines, targets of the Itararé Group and Tatuí and Corumbataí formations in the cities of Leme, Piracicaba and Tambaú were selected to study their alteration profiles, as well as for mineralogical, petrographic, geochemical and technological characterization. Field studies indicated that plastic clays occur in weathered, laminated to solids, gray to light green clayey to sandy siltstones. At the valleys, these layers are overlaid by thin alluvial deposits and have a maximum thickness of 2 meters, while on the hilltops, especially in the Tatuí Formation, the layers can be up to 6 meters thick and occur at greater depths, being overlapped by more weathered lithotypes. The main minerals of the superplastic clay layers are constituted by montmorillonite, illite, kaolinite, quartz, alkali feldspars, muscovite and generally have lower Fe2O3 contents and a higher proportion of alkali comparing to the adjacent layers. Ceramic studies indicated high modulus of rupture in dry condition (≥ 40 Kg.f/cm²) for most samples and differences in water absorption, linear shrinkage and modulus of rupture after firing at 1.120 and 1.190°C among the lithostratigraphic units. The firing colors varied from beige to gray or ivory, excepting the Corumbataí Formation from Tambaú, which showed predominantly darker and reddish colors due to the higher content of Fe2O3 oxides/hydroxides. At the end, prospective guides are discussed in order to contribute to the discovery of new deposits.
Descrição
Palavras-chave
Matérias-primas cerâmicas, Bacia do Paraná, Intemperismo, Argilas plásticas e superplásticas, Geoquímica, Ceramic raw materials, Paraná Basin, Weathering, Plastic and superplastic clays, Geochemistry